Analytical apparatus and method for smokes and gases

ABSTRACT

Smoke is passed through a moving filter tape, and the darkness of the filtered trace due to solid, non-white contaminants is readout by photo-electric means. At least one resettable counter is provided to register the number of times the smoke exceeds a smoke level for a predetermined period of time.

I United States Patent [151 3,653,773 Childs [451 Apr. 4, 1972 s41 ANALYTICAL APPARATUS AND 2,675,697 4/1954 Quynn et al. ..73/2s METHOD FOR SMOKES AND GASES 2,825,872 3/1958 Stubbs et a1. .....324/71 2,768,370 10/1956 Maninger ..356/38 X 2] Inventor: Elbert Childs, fiastings-on-fludson, 2,898,803 8/1959 Morrison ..356/38 3,088,364 5/1963 Rozsa et al ..356/38 [73] Assignee: Mobil Oil Corporation Primary ExaminerRonald L. Wibert [22] Filed 1970 Assistant Examiner-F. L. Evans [21] App]. No.: 19,584 Att0rney0swald G. Hayes, Andrew L. Gaboriault and James F. Powers, Jr.

[52] US. Cl ..356/207, 73/28, 356/38,

35 209 [57] ABSTRACT Int. Cl- ..G0ln Smoke is assed through a moving filter tape and the dark- [58] Field of Search ..356/38, 207, 209, 21 1, 212; [less f [he filte ed trace due to solid non-white contaminants 73/23 is readout by photo-electric means. At least one resettable counter is provided to register the number of times the smoke [56] References Cited exceeds a smoke level for a predetermined period of time.

UNITEPSTATES PATENTS 8 Claims, 8 Drawing Figures 2,667,779 2/1954 Von Brand ..73/28 24 25 Re ulofed Exhaust Recorder DC |2\l/)oHs Probe Power Su ppiy 2/ lo I, Photo I Cell Tape {Head 22 M l l PaperTape N /3 0 Feed 1 /6 Tape Pull /2 Motor Vacuum /7 F If Gau /8\ .8,

Cl -20 Vacuum Regulator Vacuum 5 I2Vo|ts Pump DC PATENTEUAPR 41972 3653773 SHEET 8 OF 6 FIGURE 8 IOA Fuse V ocuum Pump 204 203 Fun /205 20 Heater K205 202 20/ Time Fuse Switch Tiger Bu e w 821325 Q 208 Circuifs Common 7 Ground Inverter and 3 I, 209/ Rectifier Counters 2/0 |2v -+|2v Regulator Regulator rive lscnmma ors 2/4/ Motor Elbert 8. Chi Ids ANALYTICAL APPARATUS AND METHOD FOR SMOKES AND GASES BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to an apparatus and a method for conducting studies of the content of solid, non-white contaminants in a gas. More particularly, it relates to an apparatus and a method for indicating the quantity of soot and other solid, non-white contaminants present in the gases being discharged from a combustion chamber. Still more particularly, the present invention provides an apparatus and a method for monitoring the exhaust from a diesel engine.

2. Description of the Prior Art There are several testing devices in use in industry today from which some indication of the degree of contamination of waste gases can be ascertained. These devices generally fall into two distinct types which are briefly discussed hereinafter.

A first type can be referred to as a continuous smoke tester which operates on the principle of determining the degree of transparency of the gas by the use of photo-electric devices. A recording device is used in conjunction with photo-electric equipment so that a permanently visible record of the study is provided. The main disadvantage inherent in this type of equipment is the poor sensitivity to smoke below the visibility level. This disadvantage prevents the use of the device except in the study of gases containing an established minimum of contamination. Other factors limit their utility such as unsuitability for being transported for various applications and exacting installation requirements which render its adaptation to specific situations expensive and time consuming. Furthermore, devices of this character are delicate and require considerable attention if they are to be maintained in proper working order. v

Another type of testing device is commonly known as the spot tester. Spot testers provide a paper record from the smoke itself by causing smoke to deposit a portion of its contaminant upon a suitable paper. The means employed for doing this are of varying types. Some devices utilize an intermittently operated filter tape, the operation being either manual or mechanical. For various reasons, equipment of the spot testing type is unsatisfactory. In the first place, no understanding or indication can be derived from a single spot test as to whether or not the smoke condition that is made apparent by the spot has been continuous and constant during the taking of the record or has continuously varied from one degree of density to another. Therefore, in order to determine what conditions are taking place in a combustion chamber over a given interval of time, it is necessary to make several spot tests to indicate the changing conditions. This, of course, requires a considerable amount of time. Furthermore, it is not possible to make immediate adjustments to an engine and to observe their effects during the taking of the record. The record must first be taken and studied before any adjustments can be made, and after the adjustments are made, additional spot tests must be run in order to determine the effect of the adjustment to the engine. Oftentimes several series of tests and adjustments are necessary in order to effect the necessary corrections to the engine condition. The adjustment is difficult to make because the engine conditions are continuously changing, especially if the engine has just been started in operation because at such time the combustion chamber is cold, as is the incoming fuel, and thus combustion efficiency is lower than when the engine and fuel have become heated. Therefore, in order to obtain reliable data and to make accurate adjustments, it is necessary to allow the engine to heat up for many minutes before spot tests are completed.

Additionally, in using the spot test, if the smoke that is being examined is heavily laden with contaminants, the initial spot that is deposited is likely to be so dense as to be meaningless except to indicate that the gas is quite heavily laden with contaminants. Oftentimes, a spot test of half the time of a previously made one under substantially the same conditions will produce a smoke spot of substantially the same color and density. Therefore, it is necessary to run several spot tests of progressively shorter duration before a spot can be produced which will have a definite meaning when compared with its standard. The main disadvantage of the spot type test is that it does not afford a record corresponding to the changes that take place in a combustion chamber of a engine either as the changes are effected by reasons of the physical conditions of the engine or as effected by adjustments made thereto by the individual who is examining it, as a result of which disadvantages, accurate records and adjustments are extremely difficult to obtain, if not in many cases, impossible. There is also a good deal of condensation trouble. If spot testers are not warmed up (on furnace, or in another makeshift manner) frequently first spots are wet and soggy and must be repeated. Spot testers have been brought to a fair degree of perfection within the limits of their applicability and for those purposes usually produce satisfactory results. However, there is considerable need for an instrument of a more sensitive nature so as to permit a higher degree of perfection in the building and operation of combustion chambers and engines.

U.S. Pat. No. 2,667,779 discloses a device for drawing off and filtering a contaminated gas through a moving filter tape so as to permit an observation of the contaminant content, and the changes in the degree of contamination. However, the device of U5. Pat. No. 2,667,779 requires that the filter tape record be compared with prestandardized test tapes to determine the quantity of contaminants in the gas under test.

SUMMARY OF THE INVENTION In accordance with an aspect of the invention, there is provided an apparatus for indicating the amount of solid, nonwhite contaminant suspended in a gas comprising means for providing a stream of the gas, and means for moving a filter tape through the stream. The apparatus also includes means for generating a signal representative of the amount of contaminants filtered from the stream by the tape, and means for indicating the number of times the contaminants signal exceeds a predetermined value for a predetermined period of time.

In accordance with another aspect of the invention, there is provided a method of indicating the amount of solid, nonwhite contaminant suspended in a gas comprising the steps of forming a stream of gas, and moving a filter tape through the stream. The method also includes generating a signal representative of the amount of contaminants filtered from the stream by the tape, and automatically indicating the number of times the contaminants signal exceeds a predetermined value for a predetermined period of time.

Thus, the apparatus and method of the present invention provides for fast interpretation of results of the analysis by indicating a numerical value representative of a degree of amount of contaminants in the gas. By providing for fast interpretation, the invention is particularly useful in field investigations where compliance with smoke regulations is involved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic representation of a specific embodiment of the present invention with various components shown in block form;

FIG. 2 is a block diagram of a circuit arrangement emboding the invention;

FIG. 3 shows an inverter-rectifier circuit suitable for a specific embodiment of the invention;

FIG. 4 shows a photocell circuit suitable for a specific embodiment of the invention;

FIGS. 5 and 6 show circuits for providing regulated DC voltages;

FIG. 7 shows a circuit arrangement for indicating the number of times the contaminants signal exceeds a predetermined value for a predetermined period of time; and

FIG. 8 shows in block diagram form an arrangement for connecting a specific embodiment of the invention to a battery in a vehicle.

DESCRIPTION OF SPECIFIC EMBODIMENTS With reference to FIG. 1, filter paper 13 from a paper tape feed 10 is pulled through a tape head 11, 12 by a tape pull motor 14. The tape 13 passes from the motor 14 to a tape rewind spool 15. The tape head comprises an inflow plate 11 and an outflow plate 12. A conduit 21 interconnects an exhaust probe (not shown) in an exhaust system such as that used with a diesel engine and a bore or conduit 11 formed in the inflow plate 11. A bore or conduit 12 formed in outflow plate 12 is connected to a conduit having a filter 17 therein. The conduit 20 is connected at its downstream end to a vacuum pump 19. A vacuum gauge 16 and a vacuum regulator 18 are also connected to the conduit 20 to provide a constant vacuum in the conduit 20.

The vacuum pump 19 acts to draw exhaust from the exhaust probe (not shown) through the conduit 21, the inflow conduit or bore 11, the filter tape 13 and the outflow conduit or bore 12'. The amount of light from a lamp 23 which is reflected from the solid, non-white contaminant smoke trace on-the filter tape 13 is sensed by a photocell 22. The photocell 22 provides an output representative of the darkness of the smoke trace to a recorder 24. The recorder 24, the photocell 22, the lamp 23 and the tape pull motor 14 are connected to a regulated l2V DC power supply 25. The regulated power supply 25 and the vacuum pump 19 are connected to a l2-volt DC source, such as a vehicle battery.

To monitor a diesel engine exhaust, the exhaust probe (not shown) is suitably aligned along the axis of the exhaust stackor tail pipe at the outlet end of the system. The probe may be constructed of stainless steel and include a heat radiator to dissipate heat. The conduit 21 may be constructed from small tubing, such as 3/16-inch ID. to reduce sample flow time between the probe and the tape head 11, 12. The vacuum pump 19 is provided to further reduce the time lag due to the transfer of the sample from the probe to the tape head 11, 12. To stabilize the flow of exhaust through the system, the vacuum regulator 18 may be suitably set to provide a 4-inch Hg. vacuum indication on the gauge 16.

The tape 13 is considerably wider than the mouth of the inflow and outflow conduits l 1', 12' so that the tape 13 acts as a gasket and seals the mouth of the outflow conduit 12'. The inflow plate 11 is fitted sufficiently tightly on the outflow plate 12 to substantially eliminate leakage into the outflow conduit 12' from the atmosphere. A suitable diameter for the inflow and outflow conduits 11, 12 is three-eighths inch.

The tape pull motor 14 is powered by the regulated power supply 25 to provide a constant tape speed. A suitable tape speed is 10 inches per minute for diesel engine exhaust monitoring.

The lamp 23 and the photocell 23 are enclosed in a bored head such that the photocell 22 senses only the light reflected from the tape 13. The head may be made from black Bakelite board to provide a light path, as indicated by the dash line from the lamp 23 to the tape 13, and reflected to the photocell 22 at approximately a 60 angle.

The recorder 24 and regulated power supply 25 are shown in greater detail in the block diagram of FIG. 2. With reference to FIG. 2, the output terminals of a l2-volt vehicle battery are connected to the input of an inverter circuit 35 which changes the l2-volt DC to l20-volt AC at approximately 60 cycles per second. The 120 volt AC output of the inverter 35 is applied to a transformer 34 which provides a 36- volt AC output. The 36 volt AC output is fed to a bridge rectitier circuit 33 which in turn provides +20-volt DC and 20- volt DC outputs. The +20-volt DC output from the bridge rectifier 33 is applied to a voltage regulator which in turn provides a regulated +12-volt DC output for application to the lamp 23', the photocell 22' and to discriminator circuits 36,

40, 44. The 20-volt DC output from the bridge rectifier circuit 33 is applied to a voltage regulator 32 which, in turn, provides a regulated l2-volt DC output for application to the tape pull motor 14', and to discriminator circuits 36, 40, 44.

As described with reference to FIG. 1, light from the lamp 23' is reflected from the tape 13 to the photocell 22'. The photocell 22 simultaneously applies an output representative of the amount of light reflected from the tape 13 to discriminators Nos. 1-3, 36, 40, 44. Each of the discriminators 36, 40, 44 is adjusted to trip at a different level of output from the photocell 22'. For example, discriminator No. 1 may be set to trip when the output from the photocell 22' is representative of a smoke value 5 on a Bacharach True-Spot smoke scale, and discriminators No. 2 and No. 3 may be set to trip when the output of the photocell 22' indicates smoke values 6 and 7, respectively. Smoke values on a Bacharach True'Spot smoke scale increase as the darkness of a spot or trace increases.

When the photocell 22 applies a signal to the discriminator 36 which is representative of a smoke value of 5 or greater, the discriminator 36 actuates an electronic timer 37. The timer 37 is set for a predetermined period, for example, 5 seconds. At the end of the predeten'nined period of time, a trigger circuit 38 is actuated, and the timer 37 is reset. When the trigger circuit 38 is actuated, it applies a signal to a counter 39 to add one count to its digital output which indicates that the smoke trace on the tape 13 (FIG. 1) had a smoke value of 5 or greater for the predetermined period of time, e.g., 5 seconds. The timer 37 will continue to actuate the trigger circuit 38 at the end of each predetermined period of time to add one count to the digital output of the counter 39 until the signal applied to the discriminator 36 by the photocell 22 indicates a smoke value of less than 5. For example, if the discriminator 36 provides a signal to the 5-second timer 37 for less than 5 seconds, the timer 37 is reset and does not provide an output signal to the trigger 38.

The discriminator 40 operates in the same manner as the discriminator 36 to actuate a timer 41 when the output signal from the photocell 22 indicates a smoke value of 6 or greater. When the discriminator 26 provides a signal to the timer 41 for a predetermined period of time, e.g., 5 seconds, the timer 41 actuates a trigger circuit 42 to apply a signal to a counter 43. At this time, the timer 41 is also reset. Application of a signal to the counter 43 causes the counter 43 to add one count to its digital output which indicates that the smoke trace on the tape 13 (FIG. 1) had a smoke value of 6 or greater for the predetermined period of time. In the same manner, the discriminator 44 is tripped when the signal applied thereto by the photocell 22' indicates a smoke value of 7 or higher. When the discriminator 44 is tripped, it provides an actuating signal to an electronic timer 45 which is set for a predetermined period, e.g., 5 seconds. If the discriminator 44 applies a signal to the timer 45 for the predetermined period of time, the timer applies an output signal to a trigger circuit 46 and also the timer 45 is reset. When the trigger circuit 46 is actuated by the timer 45, it provides an output signal to a counter 47 to add one count to its digital output which indicates that the smoke trace on the tape 13 (FIG. 1) had a smoke value of 7 or greater for the predetermined period of time.

Since the photocell 22' simultaneously applies its output to the discriminators 36, 40, 44, all of the discriminators will be tripped when the output signal of the photocell 22' indicates a smoke value of 7 or greater. However, only discriminators Nos. 1 and 2 will be tripped when the output signal of the photocell 21' indicates a smoke value of at least 6 and less than 7. Similarly, only discriminator No. I will be tripped when the output signal from the photocell 22 indicates a smoke value of at least 5 and less than 6.

The timers 37, 41, 45 may be set for the same predetermined period, e.g., 5 seconds, or each timer 37, 41, 45 may be set to a different predetermined period.

The discriminators 36, 40, 44 may be set to trip at low, marginal and unsatisfactory smoke levels. For example, a standard may be that if there are no counts observed in the digital counter 39 which indicates a smoke value of 5 or above the equipment is considered to be operating at a low smoke emission level and therefore in good condition. If the digital counter 39 indicates many counts and the counter 43 indicates some counts at or above the 6 value, the engine may be considered as operating in a marginal state and should be scheduled for repair or adjustment. The standard may also provide that if any counts are indicates on the digital counter 47, the engine is operating unsatisfactorily and immediate attention is required.

The photocell 22 also provides an output signal to a meter 31. The meter 31 is calibrated in smoke values and is used to facilitate the setting of the discriminators 36, 40, 44 as will be described hereinafter.

The inverter 35, the transformer 34 and the bridge rectifier 33 are shown in greater detail in FIG. 3. With reference to FIG. 3, a 12 volt battery of a vehicle is connected across a capacitor 58 of a power oscillator which includes an inverter transformer 59 and the circuit shown to the left of the transformer 59. The power oscillator functions as the inverter 35 of FIG. 2. The left side of the capacitor 58 is connected between a pair of transistors 55, 56, a pair of resistors 52, 53, and a pair of capacitors 50, 51. The right side of the capacitor 58 is connected to approximately the middle of the transformer 59. The outer ends of the transformer 59 are connected to a pair of resistors 54, 56 which, in turn, are connected to the pair of resistors 52, 53. The transformer 59 is also connected at intermediate points to the pair of transistors 55, 56, and the bases of the transistors 55, 56 are connected to the outer terminals of the pair of resistors 52, 53 and of the pair of capacitors 50, 51. The outer terminals of the pair of capacitors 50, 51 and the pair of resistors 52, 53 are also connected to the left side of the pair of resistors 54, 57.

The inverter circuit or the power oscillator provides 120 volt AC at the secondary winding of the inverter transformer 59. This secondary winding is connected to the primary winding of step-down transformer 63 through a filter circuit consisting of capacitors 60 and 61 and inductance 62. The transformer 63 applies 35 volts AC to a bridge rectifier circuit 64 which corresponds to the bridge rectifier 33 of FIG. 2.

The bridge rectifier circuit 64 developes a +20-volt DC between its right hand terminal and a common line connected to the center tap of the transformer 63, and a 20-volt DC between the left hand terminal of the bridge 64 and the common line.

FIG. 4 shows a bridge circuit suitable for calibrating the meter 31 of FIG. 2 in smoke values. With reference to FIG. 4, regulated +12V DC power is .applied across two legs of the bridge circuit. One leg of the bridge circuit consists of resistors 70, 71 and a zero adjust trimpot 72. The other leg includes the photocell 76 and a resistor 79. The meter 73, which corresponds to the meter 31 of FIG. 2, is connected between intermediate points of the two legs and in series with a calibrate trimpot 74, a resistor 74' and a span adjust trimpot 75.

To calibrate the meter 73, the photocell 76 scans an unused white tape, and the zero adjust trimpot 72 is adjusted until the meter 73 indicates a zero smoke value. The photocell 76 is then caused to scan a black paper having a smoke value of 10, and the span adjust trimpot 75 is adjusted until the meter 73 provides a full scale excursion. The photocell 76 is then caused to scan suitable gray paper tapes for the that a hand calibrated scale may be made for the meter 73 to give smoke values ofO through 10.

After initial calibration, the meter 73 may be calibrated by causing the photocell 76 to scan an unused white tape and adjusting the zero adjust trimpot 20, and then causing the photocell 76 to scan a black calibration paper having a smoke value of IO and adjusting the span adjust trimpot 75 to give full excursion.

The use of a black calibration paper may prove to be troublesome because of the possibility of scuffing the paper when the paper is placed through the tape head 11, 12 (FIG.

1). To avoid this problem, a calibrate trimpot 74 is provided in the circuit. A pair of ganged switches 77, 78 are provided to short out the calibrate trimpot 74 and to supply a regulated +12 DC power to the lamp of the photocell system when the switches 77, 78 are in RUN position as shown in FIG. 4. When the switches 77, 78 are moved to the CALIBRATE position, the calibrate trimpot 74 is placed in the circuit and power is removed from the lamp. The calibrate trimpot 74 is set to approximate the effect of a measurement of the reflectance of a black tape having a smoke value of 10.

The calibrate trimpot 74 is initially adjusted by causing the photocell 76 to scan a black paper having a smoke value of IO and adjusting the span of themeter 73 by positioning the span adjust trimpot as described hereinabove. The black paper is kept in place under the optical head and the ganged switches 77, 78 are moved to the CALIBRATE position. The calibrate trimpot 74 is then adjusted to obtain a full excursion of the meter, Le, a smoke value reading of 10. In field use, the span calibration of the meter 73 may be checked simply by turning the ganged switches 77, 78 to the CALIBRATE position, and, if necessary, by adjusting the span adjust trimpot 75 to obtain a full excursion of the meter 73.

A suitable circuit for the +12 VDC voltage regulator 30 of FIG. 2 is shown in FIG. 5. With reference to FIG. 5, a +2OV DC from the bridge rectifier 33 (FIG. 2) is applied to a voltage dropping resistor 80. The resistor 80 is connected to a series pass compound transistor circuit consisting of a pair of NPN transistors 84, 85. The resistor 80 is also connected to a resistor 83 which, in turn, is connected to the base of the transistor 85 and the collector of an amplifier transistor 86. The transistor 86 controls the base of the transistor 85.

The resistor 80 is also connected to a series-parallel circuit consisting of capacitors 81, 88, 90, a pair of zener regulators 89, 91 and a pair of resistors 82, 87. This series-parallel circuit is connected to the emitter of the amplifier transistor 86 and supplies a reference voltage to the emitter of transistor 86. The base of the transistor 84 and the emitter of the transistor 85 are connected to a resistor 92 which, in turn, is connected to the common negative lead (ground). The base of the transistor 85 and the collector of transistor 86 is connected to a resistor 93 which, in turn, is connected to a capacitor 93'. The capacitor 93 is connected between a pair of resistors 95, 96. The base of the transistor 86 is also connected between the pair of resistors 95, 96. The circuit shown in FIG. 5 developes a regulated +12V DC across a capacitor 97 as the output of the circuit.

A suitable circuit for the 12 VDC regulator 33 of FIG. 2 is shown in FIG. 6. With reference to FIG.'6, 20V DC from the bridge rectifier 33 (FIG. 2) is applied to a voltage dropping resistor 100. The resistor 100 is connected to a series pass compound transistor circuit consisting of a pair of PNP transistors 104, 105. The resistor 100 is also connected to a resistor 103 which, in turn, is connected to the base of the transistor 105 and the collector of an amplifier transistor 106. The transistor 106 controls the base of the transistor 105.

The resistor 100 is also connected to a series-parallel circuit consisting of capacitors 101, 107, 109, a pair of zener regulators 108, 110 and a pair of resistors 102, 102. This seriesparallel circuit is connected to the emitter of the amplifier transistor 106 and supplies a reference voltage to the emitter of transistor 106. The base of the transistor 104 and the emitter of the transistor 105 are connected to a resistor 111 which, in turn, is connected to the common negative lead (ground). The base of the transistor 105 and the collector of transistor 106 is connected to a resistor 112 which, in turn, is connected to a capacitor 113. The capacitor 1 13 is connected between a pair of resistors 114, 1 15. The base of the transistor 106 is also connected between the pair of resistors 114, 115. The circuit shown in FIG. 6 developes a regulated 12V DC across a capacitor 116 as the output of the circuit.

FIG. 7 shows a circuit including a discriminator, a timer, a trigger and a counter suitable for the block diagram of FIG. 2. Referring to FIG. 7, an operational amplifier 122 carries out the discriminator function. One channel of the operational amplifier 122 is connected to point A in the photocell circuit of FIG.4 through an isolating resistor 120, and the other channel of the operational amplifier 122 is connected to a reference voltage supplied by a resistor 125, a trimpot 127, a resistor 126 and a +12V DC regulated power supply. A feedback resistor 121 is connected from the inverting input 120' to the output 124 of the operational amplifier 122, and the operational amplifier 122 is further connected to the +l2V DC and l2V DC regulated power supplies. A feedback resistor 128 is also connected from the non-inverting input 125' to the ground connection 128 of the operational amplifier 122.

A suitable-operational amplifier is manufactured by RCA and identified as CA3OI5AA. When used in the circuit of FIG. 7, CA3015A has pins 1, 2 and 3 connected to points 128, 120 and 125, respectively. Further, pins 4, 9 and 10 of CA3015A are connected to the -l2V DC regulated power, point 124 and the +1 2V DC regulated power, respectively.

When the signal from the photocell circuit at point 120' exceeds the reference signal at point 125, the operational amplifier 122 generates an output signal at point 124 and across a resistor 130 to a transistor-amplifier circuit comprising transistors 132, 133 and a capacitor 134. The base of transistor 133 is also connected to point 127 through a clamping diode 129. A resistor 131 is connected to the coil 151 of a counter 152 and serves to transmit amomentary signal to the base of transistor 133 when the counter is actuated. This signal briefly cuts off transistors 133 and 132 opening a relay 138 to reset the timing circuit as described hereinbelow. Diodes 1'37 and 153 act as protective devices to cut down relay point arcing.

The transistor amplifier 132, 133 acts to operate the relay 138, which closes a normally opened contact 135 and opens a normally closed contact 136. Operation of the relay 138 acts to start an electronic timer which comprises a unijunction transistor 143, resistors 141 and 148 and a capacitor- 142. C10- sure of the contact 135 acts to trigger element the capacitor 142 through resistors 148 and 141 from a regulated 11 volts provided by a resistor 145 and a zener diode 139 and the +12V battery of the vehicle. The other side of the capacitor 142 is connected to the common ground 127'. The size of the resistor 141 is chosen to take 5 seconds to charge the capacitor 142 to a sufficient voltage to trigger the unijunction transistor 143. Activation of the unijunction transistor 143 triggers a silicon controlled rectifier 144. The rectifier 144 carries out the function of the trigger element described with reference to FIG. 2. Triggering of the rectifier 144 causes current to flow through the coil of a relay 148 to close a pairof normally opened contacts 149, 150. Diodes 145 and 147 are connected as shown to protect the rectifier 144 from voltage spikes.

Closure of the contact 149 connects the +12V battery to the coil 151 and the protective diode 153 of the counter 152 to add one count to the counter. Simultaneously, a positive pulse is sent to the base of the transistor 133 momentarily cutting it off and releasing the relay 138. The coil 151 and diode 153 are also connected to the common ground 127'.

Closure of contact 150 acts to short the capacitor 142 and thus provide a discharge path for the capacitor. Discharge of the capacitor 142 acts to reset the timer by de-energizing the unijunction transistor 143. Thus, the relay 148 is deactivated 1 and the contacts 149, 150 return to the normally opened position.

As long as the signal at point 120' exceeds the reference signal at point 125', the counter 152 will count the number of 5 second periods that this state exists. When the signal at point 120 falls below the reference signal at point 125', the operational amplifier 122 no longer provides an output signal to transistor amplifier 132, 133, and thus, the relay coil 138 is deenergized and the contact 135 returns to its normally opened position and the contact 136 returns to its normally closed position. Closure of the contact 136 acts to short the capacitor 142 and thus provide a discharge path.

Each discriminator described with reference to FIG. 2, may be adjusted to desired smoke values after the zero-span adjustments described hereinabove. The discriminator adjustment is accomplished by placing a gray paper or tape having a predetermined smoke value under the photocell head, and adjusting a response level trimpot 127 so that the discriminator triggers at desired levels. The triggering of a discriminator may be visually observed by looking at the relay 138 to observe when it is actuated. Actuation of the relay 138 indicates that the discriminator is passing a signal representative of a set smoke value.

Alternatively, if appropriate paper standards having predetermined smoke values are not available, substitute papers may be used and rated by reference to the meter 31 described with reference to FIG. 2. These papers then can be used to adjust the discriminator response level. Thus, three FIG. 7 circuits are used to provide smoke level readings of 5, 6

and 7 described with reference to FIG. 2, and each of the discriminators are adjusted in the same manner using appropriate standards.

FIG. 8 shows in block diagram form a circuit for connecting a smoke meter constructed in accordance with the present invention to the power supply of a vehicle. A l2-volt vehicle battery is shown connected between a ground and a timer switch 200. The timer switch 200 may be provided to place the smoke meter in operation for only a predetermined period of time during operation of the vehicle. Thus, the timer switch 200 may be set to connect the vehicle's battery supply to the meter during initial operation of the vehicle for a sufficient period of time to obtain a reasonably representative indication of the smoke emission under actual operating conditions.

The timer switch 200 is connected to the smoke meter by a connector 201 which, in turn, is connected to a pair of switches 202, 203 in the smoke meter. The switch 203 is connected through a fuse to a vacuum pump 204 which was described hereinabovewith reference to FIG. 1. The switch 202 is connected to a fan 2'05 and to a heater 206 through a fuse. The fan 205 may be used within the smoke meter to provide chassis cooling. The heater 206 may be located in the tape head 1 1, 12 (FIG. 1) to prevent condensation of water on the tape, particularly in cold weather.

FIG. 8 also diagrammatically shows that the switch 202 is connected through the fuse to timer circuits 207 and counters 210. As described hereinabove with reference to FIG. 7, the vehicle battery is connected to the timer and to the counter when contacts and 149 are closed.

The switch 202 is further connected to an inverter and rectifier 209 through the fuse and a diode 208. The inverter and rectifier 209 correspond to the bridge rectifier 33, the transformer 34 and the inverter 35 of FIG. 2, and to the circuit of F iG. 3.

The inverter and rectifier 209 provides -2OV DC and +20V DC outputs to a l2V DC regulated power supply 211 (FIG. 6) and a +l2V DC regulated power supply 212 (FIG. 5). The 12V DC regulated power supply 211 provides regulated power through a switch to a tape drive motor 214 which corresponds to the motor 14 of FIG. 1. The -12V DC regulated power supply 211 also supplies power to the discriminators 215 as described hereinabove with reference to FIG. 7. V

' The +12V DC regulated power supply 212 supplies regulated power to the discriminators 215 (FIG. 7), to the photocell circuit 213 (FIG. 4) and to the lamp 216 (FIG. 4).

The smoke meter described hereinabove in the descriptive specific embodiments is particularly useful in field investigations where compliance to smoke regulations are involved. It is also particularly helpful as a tool for operators of a fleet of vehicles. The meter provides for fast interpretation of results by merely reading the digital counters. The meter is also portable and readily adapted to an engine-exhaust system. In addition to providing for fast interpretation, the meter provides a relatively permanent smoke tape record of exhaust smoke levels.

The smoke meter described hereinabove is suitable to monitor the amount of any solid, non-white contaminants in any other gas streams, such as in an oil burner stack or a jet engine exhaust, and may be modified to operate under different power supplies. For example, to monitor a oil burner stack, the transformer 34, the fan 205, and the heater 206 may be powered by a 117 VAC power supply, and an AC timing motor may be used to pull the tape.

The tape speed may be varied to about 2 inches per minute for oil burner stack or jet engine exhaust monitoring. The tape speed is set to provide a reasonably dark trace for the contamination being monitored.

FIGS. 3 through 7 include the identification of suitable components for the circuits shown therein. The numbers near each resistor without a lead line indicate the resistance value of the component in Ohms.

What is claimed is:

1. Apparatus for indicating the amount of solid non-white contaminant suspended in a gas comprising:

a filter tape,

means for providing a stream of the gas,

means for moving the filter tape at a constant speed through said stream,

means for generating a signal representative of the amount of contaminant filtered from said stream by the filter tape,

means for indicating the total number of times the contaminant signal exceeds a predetermined value for a predetermined period of time, said indicating means comprises a discriminator circuit, means for applying a reference signal corresponding to said predetermined value to said discriminator circuit, means for applying the contaminant signal to said discriminator circuit, said discriminator circuit providing a discriminator output signal, a timer circuit means set for providing a timer output signal whenever said discriminator output signal persists for said predetermined period of time, a trigger circuit means for providing a trigger output signal in response to said timer output signal, means for digitally counting the number of trigger output signals and means responsive to said trigger output signal for resetting said timer circuit means.

2. The apparatus of claim 1 further comprising at least one additional indicating means, each of the indicating means being set to indicate the total number of times the contaminant signal exceeds a different predetermined value for said predetermined period oftime.

3. The apparatus of claim 1 further comprising at least one additional indicating means, each of the indicating means being set to indicate the total number of times the contaminant signal exceeds a different predetermined value for a different predetermined period of time.

4. The apparatus of claim 3 wherein the contaminant signal generating means comprises photo-electric means for monitoring the degree of darkness of the contaminants filtered by the tape.

5. The apparatus of claim 4 wherein said photo-electric means comprises a lamp and a photocell situated on the side of filter tape upon which the contaminants are filtered.

6. The apparatus of claim 5 wherein the photocell and the lamp are positioned such that the light path sensed by the photocell is reflected from the tape at approximately a 60 angle.

7. A monitoring system for indicating the number of times a signal exceeds a predetermined value for a predetermined period of time comprising:

means for generating and detecting a signal to be monitored,

means for generating a reference signal corresponding to said predetermined value,

means for comparing said monitored value signal and said reference signal and for generating a first signal whenever said monitored value signal exceeds said reference signal,

timing means responsive to said first signal for generating a second signal whenever said first signal persists for said predetermined period of time, means for generating a third signal in response to said second signal,

means for indicating the number of third signals, and

means responsive to said third signal for resetting said timing means to begin a new period.

8. A method for generating a signal indicative of the amount of solid contaminant suspended in a gas stream comprising:

depositing solids in the gas stream upon a constantly moving filter tape,

continuously generating an electrical signal representative of the amount of solids on the constantly moving tape,

electrically converting the continuously generated electrical signal to indicate the number of times it exceeds a predetermined value for a predetennined period of time,

and digitally recording the number of times the continuously generated electrical signal exceeds the predetermined value for the predetermined period of time. 

1. Apparatus for indicating the amount of solid non-white contaminant suspended in a gas comprising: a filter tape, means for providing a stream of the gas, means for moving the filter tape at a constant speed through said stream, means for generating a signal representative of the amount of contaminant filtered from said stream by the filter tape, means for indicating the total number of times the contaminant signal exceeds a predetermined value for a predetermined period of time, said indicating means comprises a discriminator circuit, means for applying a reference signal corresponding to said predetermined value to said discriminator circuit, means for applying the contaminant signal to said discriminator circuit, said discriminator circuit providing a discriminator output signal, a timer circuit means set for providing a timer output signal whenever said discriminator output signal persists for said predetermined period of time, a trigger circuit means for providing a trigger output signal in response to said timer output signal, means for digitally counting the number of trigger output signals and means responsive to said trigger output signal for resetting said timer circuit means.
 2. The apparatus of claim 1 further comprising at least one additional indicating means, each of the indicating means being set to indicate the total number of times the contaminant signal exceeds a different predetermined value for said predetermined period of time.
 3. The apparatus of claim 1 further comprising at least one additional indicating means, each of the indicating means being set to indicate the total number of times the contaminant signal exceeds a different predetermined value for a different predetermined period of time.
 4. The apparatus of claim 3 wherein the contaminant signal generating means comprises photo-electric means for monitoring the degree of darkness of the contaminants filtered by the tape.
 5. The apparatus of claim 4 wherein said photo-electric means comprises a lamp and a photocell situated on the side of filter tape upon which the contaminants are filtered.
 6. The apparatus of claim 5 wherein the photocell and the lamp are positioned such that the light path sensed by the photocell is reflected from the tape at approximately a 60* angle.
 7. A monitoring system for indicating the number of times a signal exceeds a predetermined value for a predetermined period of time comprising: means for generating and detecting a signal to be monitored, means for generating a reference signal corresponding to said predetermined value, means for comparing said monitored value signal and said reference signal and for generating a first signal whenever said monitored value signal exceeds said reference signal, timing means responsive to said first signal for generating a second signal whenever said first signal persists for said predetermined period of time, means for generating a third signal in response to said second signal, means for indicating the number of third signals, and means responsive to said third signal for resetting said timing means to begin a new period.
 8. A method for generating a signal indicative of the amount of solid contaminant suspended in a gas stream comprising: depositing solids in the gas stream upon a constantly moving filter tape, continuously generating an electrical signal representative of the amount of solids on the constantly moving tape, electrically converting the continuously generated electrical signal to indicate the number of times it exceeds a predetermined value for a predetermined period of time, and digitally recording the nuMber of times the continuously generated electrical signal exceeds the predetermined value for the predetermined period of time. 